Shedding Light on Atoms Episode 7: Covalent Bonding Name: ________________________________ 1. (a) Single carbon atoms react with _______ hydrogen atoms to produce _________. (b) Single nitrogen atoms react with _______ hydrogen atoms to produce _________. Part A Part (c) Single oxygen atoms react with _______ hydrogen atoms to produce _________. (d) Single fluorine atoms react with _______ hydrogen atom to produce _________. (e) Neon atoms _____________________________________________________________________________ 2. Draw electron-configuration diagrams for the following atoms. (You will need to know each atom’s electron configuration; see Question 12 of the Shedding Light on Atoms Episode 6: Electron Shells worksheet.) Carbon, C Nitrogen, N Sulfur, S Fluorine, F 3. Atoms can bond together either with ____________________ bonds or with _____________________ bonds. B 4. Describe how atoms join together with covalent bonds. Use a diagram of a hydrogen gas molecule (H2) to illustrate your answer. Part Part ______________________________________ ______________________________________ ______________________________________ ______________________________________ ______________________________________ ______________________________________ ______________________________________ ______________________________________ 5. Complete the electron dot diagrams below and fill in the rest of the table. Electron Dot Diagrams for Four Simple Molecules methane, CH4 ammonia, NH3 water, H2O hydrogen (the first one has been done for you) fluoride, HF Notice in the diagram of CH4 how each shared pair of electrons occupies both shells! Draw neatly. The electron configuration of carbon is _______ nitrogen is _______ oxygen is _______ fluorine is _______ The number of H atoms that can bond with a single atom of carbon is _______ nitrogen is _______ oxygen is _______ fluorine is _______ 6. Complete the paragraph below using the words in the list. Some words may need to be used twice. Some will not be used at all. covalent Group 18 inner valence (or outer) two four eight hydrogen molecule non-metals metals A ________________ is a group of two or more atoms that are bonded together by _______________ bonds. When atoms bond together in this way, their ____________________________ shells always end up with ________________ electrons in them, with the exception of ___________________ atoms, which end up with __________ electrons in their valence (or outer) shells. Covalent bonds usually only form between the atoms of __________________ (hydrogen, carbon, nitrogen etc.). The _________________ elements are very unreactive because they already have _______________ electrons in their outer shells (or ______ in the case of Helium). www.liacoseducationalmedia.com - Shedding Light on Atoms Episode 7: Covalent Bonding Page 1 of 3 C 7. Draw an electron dot diagram of an O2 molecule and an N2 molecule. Label the double bond and the triple bond. Part Part oxygen gas, O2 nitrogen gas, N2 8. Why are oxygen and nitrogen considered elements if they are made of 2 atoms bonded together? Why is water not considered an element? ________________________________________________________________________________________ ________________________________________________________________________________________ ________________________________________________________________________________________ ________________________________________________________________________________________ 9. SINGLE BONDS: In your exercise book, draw electron dot diagrams for the following molecules (which all have single bonds only). Use different coloured atoms! Have a table of electron configurations nearby. (a) phosphine (PH3) (e) methanol (CH3OH) (b) hydrogen sulfide (H2S) (draw the S atom first) (f) ethane (C2H6, but also written CH3CH3) (c) hydrochloric acid (HCl) (draw the Cl atom first) (g) hydrazine (N2H4) (d) fluorine gas (F2) (h) silane (SiH4) 10. DOUBLE and TRIPLE BONDS: In your exercise book, draw electron dot diagrams for the following molecules. The first four have at least one double bond while (e) and (f) have one triple bond each. (a) ethene (also called ethylene) (C2H4, but also (d) nitroxyl (HNO) written CH2CH2) (e) ethyne (also called acetylene) (C2H2) (b) diazine (N2H2) (Hint HNNH) (f) hydrogen cyanide (HCN) (c) carbon dioxide gas (CO2) (Hint: OCO) D 11. Fill in rest of the table. Group Group Group Group Group 12. What is a valence electron? Part Part 14 15 16 17 18 ______________________________________ helium 2 ______________________________________ He ______________________________________ carbon nitrogen oxygen fluorine neon 6 7 8 9 10 ______________________________________ C N O F Ne ______________________________________ silicon phosphorus sulfur chlorine argon 14 15 16 17 18 13. What is an atom’s valency? Si P S Cl Ar ______________________________________ Number of Valence 7 8 ______________________________________ (outer-shell) Electrons (or 2 for He) ______________________________________ Valency (no. of bonds the atom forms) 3 ______________________________________ 14. Draw structural diagrams (also called structural formulas) for NH3, H2O, HF, O2 and N2. (CH4 has been done for you.) CH4 NH3 H2O HF O2 N2 H H C H H 15. In your book, draw structural diagrams of all the molecules in Questions 9 and 10. Remember, each shared pair of electrons is represented by one line (which represents the bond). www.liacoseducationalmedia.com - Shedding Light on Atoms Episode 7: Covalent Bonding Page 2 of 3 E 16. What is wrong with this structural formula? ________________________________________________________________________ Part Part H H ________________________________________________________________________ H C C ________________________________________________________________________ ________________________________________________________________________ H H 17. You have a gas container filled with a mixture of gases. Describe how you could determine the mass of the carbon dioxide in the container. ____________________________________________________________________________________________ ____________________________________________________________________________________________ ____________________________________________________________________________________________ ____________________________________________________________________________________________ 18. Imagine that you are a scientist in the 1860s and that you have determined the chemical formulas of the following compounds. In your book, draw structural diagrams for them, ensuring that each atom has the correct number of bonds. (For example every carbon atom should have 4 bonds. You may need to refer to the table in Question 11.) (Use a pencil!!) (a) fluoromethane (CH3F) (k) carbon disulphide, CS2 (b) difluoromethane, CH2F2 (l) formaldehyde, CH2O (c) tetrafluoromethane, CF4 (m) sulfur monoxide, SO (d) hydrogen peroxide (H2O2) (Hint: HOOH) (n) hydrogen cyanide, HCN (e) hydroxylamine, NH2OH (HINT: all single (o) dioxygen difluoride, O2F2 bonds) (p) hypochlorous acid, HClO (f) triazane, N3H5 (HINT: all single bonds) (q) isocyanic acid, NCOH (g) triazene, N3H3 (HINT: one double bond) (r) tetrafluoroethene, C2F4 HINT: No more hints! (s) ethylamine, C2H7N (h) phosphorus trifluoride, PF3 (t) cyanogen, NCCN (or C2N2) (i) ethanol, CH3CH2OH (u) urea, CO(NH2)2 (j) carbonyl sulphide, OCS (v) acetonitrile, CH3CN 19. Many compounds were found to have the same formula but different structures! Try to draw two different structures for each of the following compounds. (a) C4H10 (All single bonds: one version is called butane and the other is called methyl propane) (b) C2H6O (All single bonds: one version is called ethanol and the other version is called dimethyl ether. To help differentiate, ethanol is often written as CH3CH2OH, while dimethyl ether is often written as CH3OCH3) C4H10 C2H6O (i) (ii) (i) (ii) (Note: The study of compounds that have carbon atoms in them is called “organic chemistry”. There are literally millions of named compounds that contain carbon atoms. No other element even comes close.) www.liacoseducationalmedia.com - Shedding Light on Atoms Episode 7: Covalent Bonding Page 3 of 3 .